For 3.5" floppy disks (FD), 1.2 MB (after formatting) capacity is widely used in Japan, while 720 KB/1.44 MB (after formatting) capacity is widely used in major countries other than Japan. Data processing systems that can read/write not only 720 KB/1.44 MB FD are known, as well as systems that can read/write 1.2 MB FD. However, the prior art requires a hardware block (such as an I/O register which can be accessed by a main central processing unit (CPU) of the system unit) to be added to the system unit which can read/write 720 KB/1.44 MB FD in order to also read/write 1.2 MB FD. Furthermore, in the prior art, a cable for connecting the system unit and the floppy disk drive apparatus requires a signal line to be added for dedicating a control signal from the system unit to the floppy disk drive apparatus for causing the floppy disk drive apparatus to read/write 1.2 MB FD. Thus, a data processing system suited to 720 KB/1.44 MB capacity formatting that is modifiable into a data processing system suited to three types of capacity formatting of 720 KB/1.2 MB/1.44 MB by making only a few changes is desired.
The following are descriptions of two data processing systems, a first suited to two types of capacity formatting of 720 KB/1.44 MB, and then of a second data processing system suited to three types of capacity formatting of 720 KB/1.2 MB/1.44 MB by changing said data processing system suited to two types of capacity formatting of 720 KB/1.44 MB.
Turning first to FIG. 4, an example of a conventional data processing system which may read/write only 720 KB FD and 1.44 MB FD is shown. A system unit 1 includes a main CPU 3, a main memory 5 for storing a program including a device driver program (BIOS) 6, a floppy disk controller (FDC) 7, a group of I/O registers 9, a part or all of which are provided within the FDC 7, and a connector 11. The connector 11 has, for example, 34 pins and is connected to a floppy disk drive apparatus 31 through a two-mode floppy disk drive (FDD) cable 21, which is also called a standard FDD cable. The cable 21 is provided with multiple cable connectors (#0 and #1) so that multiple floppy disk drive apparatus 31 may be attached to the system unit 1.
The I/O registers 9 are mapped in an I/O address space of the main CPU 3. The I/O addresses are, for example, 03F1hex, 03F2hex, and so on. The program in the memory 5 contains a FDD device driver or a BIOS 6 for controlling the floppy disk drive apparatus 31 from the system unit 1 in a manner well known. The CPU 3 reads/writes bit patterns from/into the I/O registers 9 in order to communicate with the FDC 7. When the CPU 3 writes bit patterns into the I/O registers 9, the FDC 7 sends signals to a pin or pins of the connector, according to the bit patterns written by the CPU 3. When the FDC 7 writes bit patterns into the I/O registers 9 according to the signals from the floppy disk drive apparatus 31, the CPU 3 reads the bit patterns written by the FDC 7.
The floppy disk drive apparatus 31 has a connector 33, a standard logic circuit 35, a read/write circuit 36, a head 37, a stepping motor 38 for moving the head 37, a stepping motor driver 39 for driving the stepping motor 38, a spindle motor 42 for rotating a floppy disk, and a spindle motor driver 43 for driving the spindle motor 42. The rotation speed of the spindle motor 42 is adjusted to 300 revolutions per minute (rpm) in both of 720 KB mode and 1.44 MB mode. Only the speed of the data transmission between the system unit 1 and the apparatus 31 is different between 720 KB mode and 1.44 MB mode. The connector 33 is connected to the cable connector #0 or #1.
The standard cable 21 includes a pin 2 and a pin 4. In Table 1, the pin 2 is dedicated for the selection of the data transmission rate, and the pin 4 is connected to a floppy disk drive apparatus identification line. The floppy disk drive apparatus 31 operates in 1.44 MB mode (the data rate is 500 Kbps.) if a data rate selection signal on the pin 2 is in a true level, while the apparatus 31 operates in 720 KB mode (the data rate is 250 Kbps.) if the data rate selection signal on the pin 2 is in a false level. The drive identification line is dedicated for informing the system unit 1 that the apparatus 31 is active when a drive selection signal (the pin 4) is in true level.
TABLE 1 ______________________________________ Pin 2 Data Transition Rate Selection 1 Pin 4 Drive Identification ______________________________________
Turning now to FIG. 5, another conventional data processing system which operates in three modes, which are 720 KB mode, 1.2 MB mode, and 1.44 MB mode is shown. In order to operate in the 1.2 MB mode (in addition to the 720 KB mode and 1.44 MB mode), the spindle motor 42 operates at 360 rpm as well as at 300 rpm. An additional I/O register 20 is required for a system unit 101 in addition to the existing group of I/O registers 9. The I/O address of the additional I/O register 20 is one of reserved addresses, for example, 097Fhex.
FIG. 6 shows a bit definition of the additional I/O register 20. The bit 0 defines the rotation speed of the spindle motor 42 of a floppy disk drive apparatus 131 connected to the connector #1 of a three mode cable 26. The bit 3 defines the rotation speed of the spindle motor 42 of the floppy disk drive apparatus 131 connected to the connector #0. The spindle motor 42 of the FDD apparatus 131 connected to the connector #1 operates at 300 rpm for 1.44 MB/720 KB modes if the bit 0 presents 0, while the spindle motor 42 operates at 360 rpm for 1.2 MB mode if the bit 0 presents 1. The spindle motor 42 of the FDD apparatus 131 connected to the connector #0 operates at 300 rpm for the 1.44 MB/720 KB modes if the bit 3 presents 0, while the spindle motor 42 works at 360 rpm for the 1.2 MB mode if the bit 3 presents 1. A device driver program is required for the CPU 3 to read/write data from or to the register 20.
The conventional system as shown in FIG. 5 requires the cable 26 which is dedicated for supporting the three mode operation. The standard cable 21 as shown in FIG. 4 cannot be used instead of the three mode cable 26. In the three mode FDD cable 26, as shown in Table 2, the pin 2 defines the rotation speed of the spindle motor 42 of the FDD 131 connected to the connector #0, while the pin 4 defines the rotation speed of the spindle motor 42 of the FDD 131 connected to the connector #1. In FIG. 5, the pin 2 is electrically connected only to the connector #0 without being connected to the connector #1. The pin 4 is not connected to the connector #1 but connected to the connector #0. The connection point of pin 4 to the connector #0 corresponds to the connection point of pin 2 to the connector #1.
TABLE 2 ______________________________________ Pin 2 Motor Speed Selection for Connector #0 Pin 4 Motor Speed Selection for Connector #1 ______________________________________
In FIG. 5, the system has a detection means 45 and a speed changing means 46. The detection means 45 is for detecting the signal defining the spindle motor speed. The speed changing means 46 is for changing the rotation speed of the spindle motor 42 by changing the voltage applied to the motor 42. The motor works at either 300 rpm or 360 rpm in response to the signal from pin 2.
As mentioned above, in order to operate in the three modes, the conventional data processing system requires additional hardware structures as hardware modifications in system unit 101, the floppy disk drive apparatus 131, and the cable 26. The hardware modifications cause a great increase in reliability tests, which induce cost increases and lengthen development periods. Thus, there is a need for a data processing system operable in three modes by making only a few changes, which do not include the hardware changes in the system unit or the cable between the system unit and the FDD apparatus.
Further, there is a need for not only a data processing system operable in three modes by making only a few changes in the system operable in two modes, but also that a new function may be added to a floppy disk drive apparatus by making a change to only a few features of the existing data processing system.
Still further, for any peripheral apparatus other than a floppy disk drive apparatus, there is a need that a new function may be added to the peripheral apparatus by making a change to only a few features of a data processing system without making changes to hardware, especially, a system unit and an interface between the system unit and the peripheral apparatus.